Zein solution and coating composition



Passed Dec. 26, 1939 UNITED STATES 'ZIIN sow-nor: AND con'rnvoCOMPOSITION Roy E. Coleman, Chicago, 111., assignor to The zeinCorporation oi America, a corporation of Delaware No Ih'awing. Originalapplication September 21, 1939, Serial. No. 295,919. Divided and hisapplication October 11, 1939, Serlal No. 298,988

'lClaims.

This invention relates to improvements in substantially anhydroussolutions and coating compositions of zein and to methods of preparingthe same. While the present invention is applicable to the production ofsolutions and coating compositions of other prolamins, it isparticularly directed to securing substantially anhydrous solutions andcoating compositions of zein with controlled solution and gellingcharacteristics,

zein being difierentiated from other prolamlns by its unusual gellingtendencies.

This application is a division of my prior copending application SerialNo. 295,919, filed September 21, 1939.

The solutions and coating compositions of my it present invention arecharacterized by the fact that they contain either no added water oronly very slight amounts of water not in excess of about 5% and are,therefore, substantially anhydrous.

The zein used in accordance with my invention may be the commercial zeinwhich contains a small percentage of moisture in the order of about 5 toabout 8%, preferably about 8%, and is obtained in the trade in powderedform, or it may be a, specially treated substantially anhydrous zein. Inthe following description of my invention I refer by the term zein" tocommercial zein or to zein of substantially the water content ofcommercial zein unless otherwise specifically designated.

In the prior art zein coating compositions, water has been included to asubstantially extent, it being considered that the solubility char- 5acterlstics of zein required the inclusion of substantial proportions ofwater in organic solvents.

For example, as stated in the Walsh et al. Patent No. 1,966,604, theaddition of water is necessary since the low-molecular weight alcohols,alcoholethers and alcohol derivatives are not effective alone in makingsolutions of zein.

In accordance with the present invention I have found thatnon-separating, stable liquid coating.

compositions of controlled gelling characteristics, either slow gellingor substantially non-gelling,

can be prepared from zein by the aid of anhydrous or substantiallyanhydrous solvents or mixtures of suchsolvents. These coating composi- Itions, over wide range of concentrations, arestable on standing attemperatures of 80 F. and

below and do not separate even when cooled to temperatures of 50 to 70F. and somewhat below. When cooled even to temperatures as low as 10above zero or to zero, solutions or coatings prepared in accordance withthepresent inven ion (or. 131-12) V r may separate and become solid;however, on heating again .to temperatures of from about 45 to F., are-solution is effected, either without stirring or with slightstirring, and the solutions and coatings return to their normal form atthe 5 re-heating temperatures. v Y

The stable non-separating solutions andcoating compositions prepared inaccordance with the present invention may be controlled as to theirgelling characteristics, as hereinafter Sat 10 forth, and may be slowgelling or substantially non-gelling with slight tendency to. increasein viscosity; that is, to thicken or become heavier in body; and in manyinstancesthey exhibit practically no tendency to thicken or to gel overprac- 15 tical periods of time in the order of about 8 to about 6months. By virtue of these novel stable characteristics, the solutionsand coatings of my invention are not limited touse immediately or withinshort periods of time after preparation as 20 is generally the case withthe prior art solutions and coating compositions. The solutions andcoating compositions of the present invention generally remain stableand reasonably constant in their characteristics during the periodsneces- 25 sary for transportation and distribution, either a in bulk orin packages, or for storage for reasonable periods of time, and hencetheir field of applicability is greatly increased;

In accordance with the present invention, I 30 have found that solutionsand coatings of zein having the desired non-separating, controlledgelling or non-gelling characteristics may be secured-by a suitablebalance between the hydrocarbon constituents or radicals present in the35 solvent or solvent mixtures and the polar constituents or radicalspresent therein, the presence of a certain proportion of carbon-bondedhydroxyl radicals being required-to secure solvent action. The presenceof a hydroxyl group in a 40 primary alcohol radical, CH2OH, appears tobe particularly helpful in securing such action. The presence of anexcessive proportion of hydroxyl radicals or of polar radicals includingsome hydroxyl radicals causes or accelerates gelling tend- 5 encies inthe zein solution or coating; Polar radicals such as O (ether oxygen),Cl, NH2, =00 and COOH thus appear to aid or cooperate with ---OH insecuring the necessary conditions of polarity in the solvent (in whichterm I 5 include solvent mixtures in the present case) for solventaction, and in excess produce the conditions enhancing gelling. While insolutions absence of gelling or slow gelling or thickening is desirable,in the preparation of plastics rapid 5 =2 1. arsenicgellingmaybedesirable. Inthepresentcaseli am more particularly concernedwith solutions having slow-gelling or non-gelling characteristics foruse in coating compositions; 5 i. e. solutions which do not gel or whichgel or thicken so slowly as to permit normal commercial handling withoutmaterial or serious thickening or gelling.

a The proportion of hydrocarbon or non-polar radicals in the solvent orsolvent mixture should not be excessive, since too high a proportion ofhydrocarbon apparently causes insolubility and separation of the zein.The same is the case in the praence of excessively long, or largehydrocarbon radicals; e. g.C4 and higher allryl radicals; Cyclichydrocarbon radicals, however, be-

have as lower alkyl-radicals. Thus. as well appear hereinafter, thebenzyl radical acts as if it were intermediate between the methyl andethyl radicals. This is consistent with the polar characteristics ofaryl-allgyl radicals as compared with alkyl-allryl radicals. v

The deslredbalance of polar constituent radicals and hydrocarbon ornon-polar radicals in a the solvent may be secured by the use of asuitable individual compound which inherently has the necessary balance,or by an admixture of compounds which are individually not balanced tosecure proper relations in the mixture and m which individually may notbe solvents for zein.

The behavior of'such mixtures may be explained by assuming salvation ofthe zein molecules or micelles by the hydromlated constituents of themixture, with orientatlon of the hydrocarbon radicals of thehydroxylatedcompound to the exterior of the solvate complex, which maythen disperse or. disolve in the remaining constituents of the solvent.

The proportion of polar radicals to hydrocar- 40 bon or non-polarradicals which I have fond to be desirable lia within a rangewhichextends between the limits of absolute methanol on the one hand, having53% .hydroxyl and 47% hydrocarbon, and absolute ethanol on the otherhand 37% hydroxyl and 63% hydrocarbon.

This range is approximate and may vary somewhat depending on the solventor solvent mixture used. The limits of this range are, however,indicative of gelling characteristics on the one 50 hand and ofinsolubilitypn the other and, therefore, provides a close and adequateguide to enable the operator, by simple experimentation, todeterminethereqmredbalanceofpolarand ydrocarbon radicals to eifectsolution of zein in anv'solvent or mixture of solvents of a characterherein set forth. Thus absolute methanol has decldedsolvent action, buthas excessive gelling tendencies, as has also ethylene glycol, which hasan even higher proportion of OH than no has methanol; Glycerol, alsohigher in OH than methanol; shows no appreciable solvent achydrocarbonradical balance range as a guide, it

is possible, by simple experimentation, todeterminereaduythatparflcularsolven or balanced mixture of solventswhich will.pro-

. duce the solution or coating composition having I the desiredproperties and characteristics for the special purpose.

Various relatively high molecular weight alco- 6 hols, having a ratio ofpolar to non-polar radicals between methanol and ethanol are excellentindividual solvents for zein with the production of non-gelling,non-separating solutions and coatings, as set forth in my priorapplications 10. Serial No. 187,559, Serial No. 187,560, and SerialIla-188,182, which were filed as continuations-in-part of applicationSerial 'No. 158,215. The solvents of these applications includediethylene glycol, triethylene glycol, propylene glyl6 col, diacetonealcohol, benzyl alcohol, cyclohexanol and furfuryl alcohol, as well astetrahydrofurfuryl alcohol and the like. These solvents individually,-ormixtures thereof, are capable oi dissolving zein to produce solutions orI) coating compositions'which are stable againstseparation and arecontrolled to be slow-gelling or substantially'non-gelling overpractical periods of time; in many cases over from about 3 to about 6months. In the case of diacetone 9.1- as cohol and cyclohexanol, forexample, very small proportions of water, say 1 to 3%, or of methanol Aor glycol may be incorporated therewith to form zein solutions ofreduced vlscosities.

Considering the cyclic and aryl-alkyl radicals of the compounds benzylalcohol, cyclohexanol, furfuryl and tetrahydroiurfuryl alcohol, forexample, as intermediate between the CH3- and the CHaCHrradicals, itwill be noted that in all of these solvents the proportion of polarraditale (-0 or -'-OH and O) may be regarded as if it were intermediatebetween the ratios for methanol and ethanol. I have found-that any ofthe above balanced'solvents or mixtures of them may housed in or addedto other solvents or solvent mixtures, otherwise balanced orapproximately balanced, such additions being frequently deslrable. Thus,benzyl alcohol aids in securing a bright clear zein film. Inseneral,

also, these solvents may be used with various 5 proportions of ethanol.Glycol or the like, providing the ratio of hydroxyl and other polargroups to hydrocarbon radicals is maintained within the proper balance,as set forth in the following examples. so

In the following examples, when I refer to anhydrous denatured alcohol Ihave reference to the commercial anhydrous denatured alcohol of thefollowing formula:

r Per cent 5 Anhydrous ethyl alcohol.. approximately 89.3 Anhydrousmethyl'alcohol do 4.4 Ethyl acetate"; do 6.3

In these examples and in all other examples here in, the term indicatesparts by weight. at

Example 1 lopartso'fneln-aremixedwithmpartsofa solvent mixturecontaining 84% of alcohol I and 16% of diethylene glycol. The mixture is35 stirred 'and on the application of heat in the order of about 85 to95 F. for about 5 minutes, a. clear, non-separating,substantiallynon-gelling stable solution of the zein is formed. I

, Example 2 1o parts'of mixed with 20 parts of-a solvent mixturecontaining 50% of benzyl alcohol and 50% of 95% alcohol.- On stirringarid with the application of heat in the order of about 108 1 to 112 1".a non-aquarating, substantially non-1 gellingstablesolutionoftheaelninthesolvent mimisohtalnedinabolit5to8minutes.

Samples slow-gelling solution is obtained in about 8 to 12 minutes.

Emple '5 lpartsotaein aremixedwith25partsotdiethylene glycol mouoethylether and 15 parts oi propyleneglycolinasultablevessel. On stirrin andwith the application of heat in the order of about no to 140 F., astable, slow-gelling solution is obtained-in about to minutes.

l'mmple 8 10partsodaeinaremixedwith20partsofdiethylene glycol monoethylether and parts of bensylalcoholinasuitablevessel. Onstirring and withthe applicaflon of heat in the order of about to E, a stable,slow-gelling solutionisobtaincdinabout10to 12minutes.

Esample 7 10pertsolaeinaremixedwith20partsoidiethylene glycol monoethylether and 30 parts of diacetone alcohol in asuitable vessel. On stirringand with the application or heat in the order of about 135 to145 R, astable, slow-gelling solutionisobtainedinabout5to 10m'inutes.

u ble 8 10partsofaeinaremixedwith20partsoidiethylene glycol numoethylether, 12 parts of trietbylene glycol and 8 parts benzyl alcohol in asuitable vessel. On stirring and with the application of heat in theorder oi. about 120 to F., a stable, slow-gelling solution is obtainedin about 8 to 12 minutes.

, Example 9 10partsotaeinaremixedwith40partsofa solvent mixturecontaining 90% of diethylene glycol and 10% of anhydrous denaturedalcohol. In practice the zein isheated with the diethylene glycol to atemperature in the order of about 190 to 195 F; to form a solution. Thesolution is permitted to cool to about 130 to F., at which temperaturethe anhydrous denatured alcohol is added. 'I1ie resulting solution isnon-separating and substantially non-gelling.

Immplcm 10partsotaeinaremixedwith80partsofa solvent mixture containing50% of diacetone- 1 cooledtoaboutmtoF.andthe95% alcohol is then added.The resulting solution is nonseparating and substantially non-gelling.

Example 11 10 parts of zein are mixed with 200 parts of a solventmixture containing 40% of propylene glycol and 60% of 95% alcohol. Inpractice, the zein is heated in the propylene glycol to about to F. toeffect solution. The solution is then cooled to about 130 F. and the 95%alcohol is then'added.- The resulting solution is non-- separating andsubstantially non-gelling.

Example 12 10 parts of zero are mixed with 20 parts of ethylene glycoland 20 parts of diethylene glycol.

- 0n stirring-and with the application of heat in the order of about toF., a clear, nonseparating, substantially non-gelling stable solution ofthe zein in the solvent mixture is obtained in about 8 to 12 minutes. 4

Example 13 10 parts of zein are mixed with 80 parts of benzyl alcoholand 20 parts of ethylene glycol in a suitable vessel. On stirring andwith the application of heat in the order of about 130 to 150 F., astable, slow-gelling solution is obtained in about 5 to 10 minutes.

Example 14 10 parts ofaein are mixed with '70 parts of propylene glycoland 30 partsof glycerlne in a suitable vessel. On stirring and with theapplication of heat in the order of about 140 to 160 F., a stable,slow-gelling solution is obtained in about 8 to 12 minutes.

Example 15 10 parts of zein are mixed with 48 parts of diacetone alcoholand 12'parts'of ethylene glycol in a suitable vessel. On stirring andwith the application of heat in the order of about 160 to 170 F. astable, slow-gelling solution is obtained in about 5 to 10 minutes.

' Example 16 10 parts of zein are mixed with 32 parts of triethyleneglycol and 8 parts of glycerlne in a suitable vessel. On stirring andwith the application of heat inthe order of about 120 to 130 F., astable, slow-gelling solution is obtained in about 10 to 12 minutes.

Solvent mixtures of non-gelling or controlled gelling characteristicsmay be produced by mixingmiscible compounds having a deficiency ofhydroxyl or polar radicals with compounds having a balance or an excessthereof to secure the desired balance or polar and hydrocarbon radicalsin the resulting mixtures. An extreme example of the production of suchsolvents is the admixture of toluene (a non-solvent for zein) andmethanol. Mixtures of methanol and toluol containing 5 to 45% of toluolare excellent solvents for zein, and have retarded and in somecasesrelatively slow-gelling tendencies. The preferred range is 35 to45% toluol. The follow- .ing examples are illustrative of such mixtures.By the expression retarded gelling tendencies as used in these examplesand elsewhere throughout the specification, I mean solutions of zein insolvent mixtures which have retarded gelling tendencies with respect..to the gelling time of solutions of zein in the constituent of themix-'- ture of solvents having a tendency to form a gelling zeinsolution.

Example 17 parts of zein are mixed with 40 parts oia mixture consistingof about 55% of methanol and about 45% of toluol. On stirring and withthe application of heat in the order of about 100 to 105 F., anon-separating, stable solution 01' the zein inthe solvent mixturehaving greatly retarded gelling tendencies is obtained.

Example 18 10 parts of zein are mixed with 24 parts of anhydrousisopropyl alcohol and 6 parts of C. P. glycerine in a suitable vessel.On stirring and with the application of heat in the order of about 115to 125 F., a non-separating, slow-gelling, stable solution of the zeinin the solvent mixture is obtained.

Example 19 Example 20 10 parts of zein are mixed with 18 parts ofmethanol and 22 parts of benzol in a suitable vessel. On stirring andwith the application of heat in the order of about 90 to 110 F., anonseparating, stable solution of the zein in the solvent mixture havingretarded gelling tendencies is obtained.

Example 21 $9 10 parts of zein are mixed with 125 parts of a solventmixture containing of cylclohexanol, 40% of 95% alcohol,- 10% oi toluol,and

' 10% of linseed fatty acids. In practice, the zein is heated in thecyclohexanol to about 190 to 200 F., to eflect solution. The solution isthen cooled to about 130 F.,- and the other ingredients are added. Thesolution formed is stable and non-gelling.

Anhydrous or substantially anhydrous solvents may be prepared from thealiphatic alcohols having from 2 to 4 carbon atoms by adding theretohydroxylated or polar compounds having higher ratios of OH or polargroups (including CO, --NH:, O- or OH) than ethanol to secure thedesired balanced relations between polar and non-polar groups. Thesimplest monoand polyhydric alcohols are particularly useful in thisconnection, these being methanol, glycol and glycerol. The followingexamples are illustrative of zein solutions prepared with such solventmixtures in accordance with my invention.

Example 22 10 parts of zein are mixed with 40 parts of a solvent mixturecontaining 86% of 95% alcohol and 14% of ethylene glycol. The mixture isstirred and on the application of heat in the order of about 90 to 95 E,a clear, non-separating, slow-gelling, stable solution of the zein inthe solvent mixture is i'ormed.

Example 23 10 parts of zein are mixed with 40 parts of a solvent mixturecontaining 89% of 95% alcohol and 11% oi dichlorethyl ether. On stirringand arcane with the application oi heat in the order of about to 85 1 anon-separating, substantially slowgelling, stable solution 01' themixture is obtained.

Example 24 Example 25 10 parts otzein are mixed with 30 parts of asolvent mixture containing 50% oi ethylene glycol monomethyl ether and50% of anhydrous denatured alcohol. On stirring and with the applicationof heat in the order of to 1"., a

stable, non-separating slow-gelling solution isobtained.

Example 26 10 parts of zein are mixed with 40 parts oi a solvent mixturecontaining 84% anhydrous denatured alcohol and 16% of ethylene glycol.The mixtureis stirred and on the application of heat in the order ofabout "to F., a clear, nonseparating, slow-gelling, stable solution 01'zein in the solvent mixture is obtained.

Example 27 10 parts of zein are mixed with 30 parts of zeininthesolventanhydrous isopropyl alcohol 8.111120 parts oi. C.

P. glycerine in a suitable vessel. On stirring and with the application01' heat in the order oi about to 125 F., a non-separating,slow-gelling, stable solution of the zein in the solvent mixture.

is obtained.

Example 28 10mm of zein are mixed with as parts of 95% isopropyl alcoholand 5 parts of ethylene glycol in a suitable vesseh' On stirring andwith the v application of heat in the order of about 110 to F., anon-separating, slow-gelling, stable solution of the zein in thesolventmixture is obtained.

. It is apparent that'ethylene dichloride, tetrachlorethylene and thelike may be used in lieu oi dichlorethyl ether in the above examples. Itis also apparent, in accordance with the present invention, that theproportions of these materials used in admixture with the low-molecularweight alcohols must be controlled so that the desiredbalanced-relations between polar and non-polar groups are secured. w

. "I'he solvents and solvent mixtures for zein set forth above, as wellas other solvents or solvent mixtures which will be apparent from theforegoing, and the resulting solutions prepared in accordance with thepresent invention are substantially anhydrous, containing not more than5% of added water and, preferably, substantially ,less. The proportionsof water, permissable are thus limited in order to secure the desiredsolution characteristics and control-of gelling, since it has been foundthat the presence of water in excess of the proportions above indicateddisturbs the balance of the solvent, tending to pro-- duce or toaccelerate gelling, as well as to impair the character of the zein filmdeposited from the solution. Possible explanations of the behavior ofwater may be made on the basis that it acts as a highly polarconstituent when present in solution in excess, that it tends to causesolvaticn or hydration of the zein, and its tendencytocausegelllngmayalsoberelatedtoitshigh surface tension. The permissibleproportion may vary in various solvents or solvent mixtures, the maximumpermissible being represented by the permissible proportion of 5% in thecase of ethyl alcohol or the ethyl alcohol constituent of the solvent.Since ethyl alcohol with 5% water is a solvent producing stable solutionin only limited cases, as set forth in my application Serial No.l58,215, and in all other instances is but one constituent of a mixture,it will be apparent that the solvents prepared in accordance with thepresent invention contain (except in those specific instances)substantially less than 5% of added water.

The extent of the effect of water and the permissible proportion thereofvaries with the solvent or solvent mixture and, in general, the moreclosely the solvent or solvent mixture approaches the desired balance ofpolar groups and hydrocarbon constituents; the less the permissibleproportion of water to avoid the introduction of excessive gelling orinsolubllity. In some cases small proportions of water below the limitsabove set forth may be advantageous. 'The maximum permissible proportionmay be readily determined experimentally in each instance and in manycasesmaybeaslowas2 or3%.

By the term substantially anhydrous, in connection with solvents orsolvent mixtures, as used herein, I mean having insufiicient water inthe solvent or solvent mixture to disturb the balance thereof andintroduce excessive gelling or insolubillty, and having in no case morethan 5% water.

By the use of anhydrous or substantially anhydrous solvents or solventmixtures in accordance with my invention, I am thus enabled to preparesubstantially non-aqueous zein solutions and coating compositions whichcontain no added water, or only slight amounts thereof, not in excessof'5% and, preferably, less. By virtue of this low added water content,the field of applicability of the coating compositions and solutions inaccordance with my invention is materially widened beyond that of theaqueous coating compositions of the-prior zein art. In addition, thefilms deposited from my coating compositions and solutions have none ofthe serious drawbacks as to brittleness, lack ofluster and gloss andblooming and blushing tendencies of the-films deposited from the aqueoussolutions or coating compositions of the prior art.

Certain anhydrous or substantially anhydrous compounds or mixtum ofcompounds in accordance with my invention, characterized in having abalance of polar and hydrocarbon radicals approaching that of ethanoland bordering the desired range, have been found to be excellentsolvents for zein. Solutions or coating compositions formed by the aidof these solvents are stable against separation of the zein and producesolutions in which the gelling tendencies The quantity of anhydrous orsubstantially anhydrous solvents or mixtures of solvents necessary toprepare the desired solutions or coating compositions in accordance withmy invention may vary rather widely from about 2 to 20 or more and,preferably from about 2 to about 9 or more parts by weight of thesolvent to 1 part by weight of the zein. In most instances, 3 to 5 partsby weight of the solvent to one part by weight of the zein has beenfound sufficient to dissolve the zein and form the desired stablesolutions or coating compositions. The viscosity and gelling tendenciesof the solutions or coating compositions prepared in accordance with myinvention are at least in part dependent on the proportion of solventused. I

The co'ating compositions embodying my invention have the unusualproperties, particularly when heated, of being able to give up theirsolvent or solvents readily when applied to any surface to quickly andreadily form tough, flexible, non-tacky, hard and generally transparinaccordance with my invention are very strong and have unusual adherentproperties. In these coating compositions the film forming propertiesthereof can be built up to produce a'fllm of greater toughness,flexibility, hardness and gloss than is capable of being formed fromcoating compositions containing added water in an amount greater than 5%as in the prior art. Under normal temperature conditions, the solutionsor coating compositions in accordance with my invention will producenon-blushing coatings on drying, without the aid of supplementaryanti-blushing agents as in the prior art.

The coating compositions in accordance with my invention 'may be appliedto any surface and they may be used for coating, sizing, or impregnatingany material, such as paper, textiles, wood,

wood pulp and the like; When coated on paper, Cellophane, glass and thelike, a film is formed almost immediately which possesses the filmcharacteristics set forth above. Since these coating compositions havedecided adhesive properties, they may be used either per se'or incombination with other materials for uniting or laminating paper, cloth,wood, glass, felt, Cellophane, metals and metal foils and the like.

The characteristics of the coating compositions in accordance with myinvention, and hence of the ultimate films formed therefrom, can bealtered at will and as desired by the inclusion of diluents, modifiers,plasticizers, resins, cellulosederivatives, fillers and the like all asset forth in substantially anhydrous mixture of solvents comprising anorganic compound having a proportion of polar to non-polar radicalswhich is greater than the proportion of polar to nonpolar radicals ofethanol and an organic compound havinga proportion of polar to nonpolarradicals which is less than the'proportion of polar to non-polarradicals ofethanol, said solvents and said composition containing not inexcess of 5% of added water, and said composition being stable againstseparation of the zein at temperatures of F. and being relativelynon-gelling.

2. A substantially non-aqueous liquid coating composition comprising asolution .of zein in a substantially anhydrous mixture of solventshaving a proportion of polar to non-polarradicals which lies within arange extending between the limits oi. the proportion of polar tonon-polar radicals of methanol and the proportion 01' polar to non-polarradicals of ethanol, 5 said mixture of solvents comprising an organiccompound having a proportion oi polar to nonpolar radicals which isgreater than the proportion of polar to non-polar radicals 01' ethanoland an organic compound having a proportion of polar to non-polarradicals which is less thanthe proportion oi. polar to non-polarradicals of.

ethanol, said solvents and saidcomposition containing not in excess 015% of added water, and

said composition being stable against separation of the zein attemperatures of 70 F. and being relatively non-gelling.

3. A substantially non-aqueous liquid coating composition comprising asolution of a prolamin in a substantially anhydrous mixture of solventshaving a proportion of polar to non-polar radicals which lies within arange extending between the limits oi the proportion of polar tonon-polar radicals of methanol and the protion of the prolamin attemperatures of 70 F.

and being relatively non-gelling.

- 4; A substantially non-aqueous liquid coating composition comprising asolution of zein in a substantially anhydrous mixture of solvents havinga proportion of polar to non-polar radicals which lieswithin a rangeextending between the limits oi the proportion 01' polar to non-polarradicals of methanol and the proportion of polar to non-polar radicalsof ethanol,

.said mixture of solvents comprising methanol and toluol, said solventsand said composition containing not in excess of 5% oi added water, andsaid compositionbeing stable against separation of the zei'n attemperatures of 70 Hand being relatively non-gelling.

5. A substantially non-aqueous liquid coating composition comprisingasolutionot zein in a substantially anhydrous mixtureoi solvents having aproportion of polar to non-pol'arradicals which lies within a rangeextending between the I.

limits of the proportion ofpolar to non-polar substantially anhydrousmixture of solvents having a proportion oi polar to non-polar radicalswhich lies within a range extending between the limits of the proportionof polai to non-polar radicals oi methanol andlthe'propor- 'tion ofpolar to non-polar radicals of ethanol,

said mixture of solvents comprising methanol and benzol, said solventsand said composition containing not in excess of 5% 01' added water, 25and said composition being stable separation of the zein at'temperaturesoi!v F: and being relatively non-gelling. v

7. The method 0! preparing a substantially non-aqueous zein solutioncontaining not in ex- 30 cess of 5% of added water which is stableagainst separation of the zein at temperatures of 70 F. and which isrelatively non-gelling, comprising mixing an organic compound having aproportion of polar to non-polar radicals which is a greater than theproportion ot polar to nonpolar radicals oi! ethanol with anorganic-compound having a proportion of polar to non-polar radicalswhich is less than theproportion of polar to non-polar radicals ofethanol to; form a solvent mixture having a proportion of polar tonon-polar radicals which lies withina range extending between the limits0! the proportion of polar to non-polar radicals of methanol and theproportion of polar to non-polar radicals of ethanol and dissolving zeinin said solvent 45 mixture to form said solution, said solvent mix-.ture containing not inexeess of 5% -01 added ROY E. COLEMAN. o

